Copy stable/11@r303970 to releng/11.0 as part of the 11.0-RELEASE
cycle.

Prune svn:mergeinfo from the new branch, and rename it to RC1.

Update __FreeBSD_version.

Use the quarterly branch for the default FreeBSD.conf pkg(8) repo and
the dvd1.iso packages population.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Adopt to current and other changes:
use dedicated kernel files with some local settings
use mkimg for ISO building
put images into separate directory and rename them for better consistency

- Build disk image (for USB sticks) and iso image
- Change name to reflect this
- Install all kernel modules
- Choose image size that i386 and amd64 can be combined into one image
- Mount tmpfs over /boot/zfs for zpool imports

- simplify by using one build script
- use label for mounting
- use GENERIC kernel
- create empty Pkg directory

Add files to build i386/amd64 bootable rescue ISO images using the
nanobsd framework.